My car’s check engine light come on when I pressed down the gas pedal, and goes away when I release the gas pedal. This has been continue for awhile. I check the posting and follow the instruction to pull the code. I got 13, which corresponding to the pressure sensor (intake manifold). I took a look at the sensor, which is located at the wheel well area on the passenger side under the hood. From visual inspection, the sensor seemed OK. There is a plug connected to the sensor in which I believe it is connected to the ECU. I want to measure the voltage coming off from this sensor, but have no reference. Does anyone knows how to do it or has similar pressure sensor problem and know how to fix it?

When we first got the car in September, this pressure sensor problem does not exist (the engine light did not come on); it came on one day after I have changed the drive belts. Well, this does not seem to make sense to me, because I did not I touch everything else. Does anyone know if there is something (some parts) I may have accidentally touched during the drive belts installation and causing this check engine light problem?

Thanks in advance.

 

Check the boost sensor voltage at the ECU, that way you're checking the entire circuit, not just the boost sensor. Use the link below.

My boost sensor code comes on every time I romp on her, it's like a normal thing for me ever since the wide open exhaust went on her. I have a vac leak I need to get fixed this weekend, so that may help, I dunno. That's the only advice other than the ECU checks I can give you- check for vac leaks

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/troubleshooting-your-car-ecu-340578/

 

Yeah, I agree about checking for vac. leaks...also there is a vac. line that goes from your boost sensor to your intake manifold, make sure it's connected well at both points. Good Luck!

 

The line on the N/A is right in front of the bottom of the upper intake manifold, just above the ACV there are two vacs, ignore them. The one you want is right in the middle of the bottome of the UIM, can't miss it.

 

I dont much about the causes of code 13, but on my n/a when i drove on cold days it would do that, im assuming b/c i had a cone filter. when i drove with stock intake it didnt do that. if you have an upgraded intake then that is most likely the cause, i dont think there are any detremintal(sp...been a long day) effects. so in other words if you cant find any cause as stated above its the intake.

 

Thanks guys for the information. Several things I did not understand. Why vacuum leak will affect the pressure sensor reading? (I know nothing why car engine need vacuum, any oneline source that teach car engine basics?) Would the air intake pressure, which is monitored by the pressure sensor, is the same the the atmospher pressure that we are experiencing in the envirnoment. Or the air compression process inside the engine that creates a difference in air pressure between the inside of the engine and the outside; thus, a suction force created and air rush into the engine through the intake manifold. And this is the engine vacuum behaviour that people referering to? Could someone give comments about this?

By the way, several abberiation needs explaination:
- B/C
- N/A
- ACV
- UIM


My car has a cold air intake and a K&N cone filter. That would be the possible cause as suggested by "ajsuper7" . I will check the vacuum leaks & the ECU suggestion from the others, may be this weekend, school is keeping me busy.

Thanks guys.

 

B/C - Because
N/A- Normal Aspiration, means non-turbocharged or non-supercharged
UIM- is the upper intake manifold

You do live in cold climates and what is happening to your car sounds exactly like what happens to my rx7's when it gets below 50 degrees (f). I think the pressure sensor readings are set in a certian range and when you modify the intake really cold air throws the sensor off(goes outside the readable ranger for the sensor), i do not believe it hurts performance or is bad for the car. It is annoying but is probably normal.

 

Some basics…
The ECU uses the pressure sensor & TPS (throttle position) signals to modify the fuel delivery from the AFM (air flow meter) default.
For example cruising: TPS almost closed, pressure medium vac = go closed loop with the oxygen sensor.
Deceleration: TPS closed, pressure at high vac = fuel cut until revs drop below 1500.
Acceleration: TPS open, pressure near 0, = high load = add some extra fuel & work the aux ports & VDI as revs increase.

The ECU expects the pressure signal to drop when the TPS says you opened the throttle.
If not, it signals a check code 13.
There should be a small orifice pill in the pressure sensor line to keep spikes down & smooth out the signal.
Also any vacuum leak in or near the sensor or its hose may cause a check 13.
And of course a bad sensor or connector could be the cause.

 

I have an unrelated question about the fuel cut until 1500 rpm. When I get off the throttle and slow down it is fine until I hit around 1500 rpm at which point the car starts to jerk a little bit front and back. It seemed to get better once I got my TPS adjusted correctly, but it still does this to some extent so I always just put the car in neutral or hold the clutch till it's time to accelerate again. Is this normal behavior or could it be a problem?
Patrick

 

I had a similar condition when I swapped motors 3 months ago.
I offset the TPS setting up just a bit, and it smoothed right out.
It also goes closed loop more now.

Maybe experiment with a slightly higher setting.

 

DP

 

thanks sureshot, will give that a try
Patrick

 

I had a similar problem. I fixed it by removing the little orifice pill inside the vaccum going to the pressure sensor. It look jamed. Everything seems ok right now !

Nic

 

Changed my AFM and everything seems ok so far !